The present invention relates to data storage, and more particularly, to a tape header scheme for use in a tape storage subsystem.
In modern magnetic tape storage devices, data which is written on the tape is protected by one or more error correction code (ECC). For data correction, data which is read from the tape is conceptually arranged into a large matrix and is protected by two orthogonal error correcting codes, referred to typically as C1 and C2. The large data matrix is referred to as a sub data set (SDS). The C1 code is used to correct the rows of the SDS and the C2 code is used to correct the columns. This error correction methodology is very powerful. However, in order for this error correction methodology to work, the data has to be placed into the correct locations in the SDS. If the data's location cannot be determined, then the error correction methodology cannot be applied to this data. Therefore, the data location information is stored in a field called the header.
In one relatively new platform, a method of protecting the headers is implemented in order to provide more reliability as to the information stored in the headers. This method improves tape drive performance significantly over previous tape drive generations; however, this method does not provide the greatest of protection for the header information. Accordingly, a more reliable way to protect header information and to determine locations of data within a SDS would be very beneficial to reading data from magnetic tape.